The size of performance effects caused by exposure to inorganic lead was determined by a meta-analytical procedure. Twenty-two studies covering exposure conditions of <70 microg/100 ml blood lead concentration were considered as to whether the methods of recording performance deficits were comparable. As a consequence of different test procedures and insufficient documented test results only 13 tests out of 12 studies could be included in the analysis. For the tests Block Design, Logical Memory and Santa Ana performance deficits were found, which may be interpreted as 'small' effects in accordance with a convention for evaluating effect sizes. For the example of Block Design it could be shown that these effects are nevertheless serious. The extent of the exposure related decrease of performance was comparable with those changes of performance which can be expected during aging of up to 20 years. Subsequently, a blood lead concentration of 70 microg/100 ml cannot be considered as a safe limit against long-term decreases of psychological performance.